The present invention relates generally to packaging semiconductor devices and more specifically systems and methods for packaging multiple semiconductor devices using a single heatsink.
The demand for increased performance from computer hardware often requires processor (CPU) and application specific integrated circuit (ASIC) designers to place multiple components (e.g., memory controllers, caches, DC-DC converters, ASICs, application specific standard product (ASSPs) etc.) in close proximity to CPUs on specialized “daughter” module circuit cards. The daughter module circuit cards interface with the system motherboards.
FIG. 1 shows a typical multi-package module (MPM) 100. The MPM includes multiple components 102A-C, 104, 106, 108, 110 mounted on the module circuit card 130. Each of the components has a corresponding, individual packaging (i.e., substrate 112, 116, 118, 120, lid 122, 126, 128, respectively, etc.). FIG. 2 shows a typical multi-chip module (MCM) 200. The MCM includes multiple components 202, 204, 206, 208 mounted on a module circuit card 230. Each of the components 202, 204, 206, 208 are individually unpackaged (i.e., do not include a corresponding lid, full heatsink, etc.). The use of MCM/MPM technologies helps hardware designers leverage advances in technology while also using high speed data and power buses without compromising on signal trace lengths, thereby delivering compute performance.
One of the key challenges facing the thermal engineer in designing cooling solutions for MPMs/MCMs is the ability to transfer the heat away from each of the multiple, closely placed sources 102A-110 and 202-208. FIG. 3 shows a typical cooling solution 300 for the MPM 100. The cooling solution 300 accounts for normal manufacturing and assembly tolerances in the various package and module stacks by having varying thermal interface material (TIM) 302, 304, 306, 308, 310 thicknesses (referred to as bondline thickness). Unfortunately, an optimal bondline thickness of the TIM 302, 304, 306, 308, 310 cannot be maintained due to the various package heights. The optimal bondline thickness is the thickness in which the TIM 302, 304, 306, 308, 310 can best conduct the thermal energy from the respective sources 102A-110 to the heatsink 330. As a result, the respective sources 102A-110 are not reliably and consistently cooled. This problem is significantly exacerbated when the physical dimensions of the MPM 100 or the MCM 200 are relatively large (e.g., when there are multiple heat-producing devices that are closely placed over a large area).
The preceding problem of ineffective heat transfer is not restricted to the MPM 100 or the MCM 200. Similar problems also exist for packages and dies mounted to circuit boards. For example, due to the assembly process a package interface (i.e., lid surface for lidded packages, die surface for lidless packages) through which heat transfer must occur may not be coplanar with the heatsink base. The lack of co-planarity with the heatsink base can be caused by normal production tolerances.
In view of the foregoing, there is a need for an easily produced cooling solution that can be used for multiple package thicknesses and multiple package areas and distributions throughout a single larger area while substantially compensating for any lack of co-planarity and also substantially maintaining an optimum bondline thickness for the TIM.